Beyond the Void
by Stelra Etnae
Summary: Those who bear the D in their names are said to have inherited the bloodline of the hero king who united the world in a peace that lasted for thousands of years. But darkness lurks beneath the surface, and the outcast Twenty Kingdoms rise again to reclaim their heritage. (Great Kingdom / Void Century AU set during the canon timeline)
1. Prologue

_**This AU idea has been bouncing around in my head for a fair while now, and I'm looking forward to finally putting it into words.**_ _ **I can't guarantee that I'll be able to update this very quickly though, as I'm going to be getting quite busy with exams and coursework very soon.**_ _ **But I thought it'd be cool to get the prologue out and see what you people think of it, and continue later once I have more time.**_

 _ **I hope you like it!**_

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" _It's a name that people have secretly been inheriting in many parts of the world. And in a certain place, they called the D. clan this – 'God's Natural Enemy'."_

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 **Prologue**

"Thousands and thousands of years ago, there lived a great king who had a dream to unite all the seas in peace. His full name has been lost to the passage of time, and we know him simply by the name 'D'. King D travelled the seas, sailing from island to island, where he gained the people's trust and respect. He settled disputes with wisdom and fairness, soothing discontent and leaving good men, trusted vassals, to continue his legacy in his wake.

For months, years, he sailed through the seas – the Blues from East to South, then West to North, before returning to Grand Line where he had been born. There he formed the core of his kingdom at the heart of the sea; on an island close to the great mountain where all the seas joined as one at its peak. That island he named Raftel.

As a gentle and just ruler, King D was loved by his subjects, and so came to all the seas a great era of peace and prosperity. But time is not a gentle mistress. King D had not been a young man when he started his rule, and soon white hair began to overcome his black. Knowing that his time would eventually come to an end, he called upon his five sons to come before him.

His youngest son, Monkey, he told to set sail for East Blue, with its calm seas and gentle folk; his second youngest, Portgas, to South Blue with its warm climate and equally warm people; his middle child, Jaguar, to West Blue, the land of knowledge and scholars; his second oldest, Trafalgar, to North Blue with its icy lands and strong-willed people. And finally, his oldest son, Gol, remained to rule in Raftel and the Grand Line. They each kept the name 'D' to honor their father, and passed that name down to their descendants along with their own.

The peace brought by the Kingdoms of D lasted for thousands of years, but then came the uprising of the Twenty Kingdoms. These twenty vassals, each a descendant of those whom King D had made kings in their own lands, now resented having to bow before the Kingdoms of D. In their rebellion they brought never-before-seen weapons, a great evil that could shatter whole islands within seconds. Faced with this threat, the Kingdoms of D called upon their own guardians to come forth in combat.

From the sea came Poseidon, a mermaid princess with a voice that could reach the ears of the great Sea Kings. From the land came Pluton, a magnificent warship built by a hundred of the most talented shipwrights of Water 7. And from the sky came Uranus, a great creature of flight whose wings shone with eternal light and rained flame down upon their enemy. Together they subdued the Twenty Kingdoms' weapons, bringing the war to an end.

Their tasks done, Poseidon returned to the sea with her people; Pluton was hidden where no man could easily reach; and Uranus rose back to the skies to fly free. And thus the seas returned to peace, continuing for many centuries after that and it is to be hoped that this peace shall last for many more."

Queen Rouge finished her tale, amused when she looked over at the bed to find bright eyes still staring at her over the covers. She leaned over to press a kiss to her son's forehead. He squirmed and made the token protests every ten-year-old boy seemed to make, insisting that he was a big boy now, but couldn't fully hide his responding smile.

"Soon it will be your duty to keep the peace, so you must grow up well and become a good King like your father and grandfathers before you. But now it's time for sleep. The Reverie will be starting in a few days, and I remember that Luffy and Sabo are arriving tomorrow. You'll want to be awake for that, I believe."

At the reminder, Ace's face lit up even brighter than before, already imagining all the fun they would have over the next few days. Rouge chuckled warmly, tucking the covers against his chin. He leaned into her touch as she slid her hand up to gently brush away a stray lock of hair that had fallen into his face.

"Good night, Mum."

"Sweet dreams, my child."

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 _ **Please review and let me know what you think of this first chapter and the AU in general!**_


	2. The Story Begins

_**Thanks for all the lovely reviews and support towards this story, I'm so glad you're interested in the idea of this AU!**_

 _ **Because I'm procrastinating on doing my coursework, you get a new chapter. So be happy to benefit from my bad working habits, y'all.**_

 _ **The fic's main character listings will be shifting every now and then, particularly in the early stages as new characters get introduced and depending on the importance of each character's role in the bigger scheme of things. The ASL trio will ultimately still be central to this story, however.**_

 _ **The first few chapters in this story will be setting up the background for this AU world and for the bigger events coming later.**_ _ **I hope you'll like the big and small changes that this AU verse brings as much as I enjoyed writing them! Onward to the story!**_

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 **Chapter 1 – The Story Begins**

Ace bounced impatiently on the balls of his feet as he watched the dragon-headed royal galleon from East Blue sail into the docks, the great ship progressing at what seemed like a snail's pace. But they were finally, _finally_ here! Ace's grin split his face as he caught sight of the two familiar heads peeking over the ship's railing, one black and one blond. Spotting him as well, the pair started to wave energetically, the younger boy even springing up and down in his excitement.

"LUFFY! SABO!"

"AACCCEEEE!"

The excitable younger prince barreled towards him the moment the gangplank was set down, dodging past the legs of all the adults filing off the ship in a black and red blur. The seven-year-old boy leapt straight for Ace, knocking them both over with the force of his tackle. Ace laughed loudly, hugging his friend back just as tight.

A flash of blond and blue made Ace glance up to see Sabo jogging over to them at a much more controlled pace. But the wide grin on the other boy's face betrayed the same infectious excitement, and Ace grabbed him the moment the blond boy got within reach, pulling him unceremoniously into their mess of a human dogpile. Sabo burst out laughing even as he toppled, turning deftly to elbow Ace in his unprotected side in retaliation. Below them, Luffy complained loudly that he was getting squashed, but given how he was still giggling like a madman as he said this the protest only earned him a fond pat on the head from both older boys as they grinned at each other.

Sabo was King Dragon's young protégé, the son of a minor noble taken into the Monkey D royal household as a playmate for the young prince. Their first meeting had been outside anyone's predictions. Sabo, then seven-years-old, had been brought along to the palace with his father for an audience with the King. Told to stay in the waiting room, the boy found himself unexpectedly accosted by a boisterous four-year-old sporting a wide smile that stretched across his face. When Makino, Luffy's nanny, had gone in search for the young prince and finally located him in the waiting room, she'd found Luffy chattering at a mile a minute to a slightly bemused Sabo. Luffy had almost thrown a fit when it was time for Sabo to leave, placated only by the promise that Sabo could come back to play the next day. One day turned into another and yet another, and the blond boy practically became a permanent fixture in the palace under the young prince's insistence. This arrangement was only cemented when the then-Crown Prince Dragon, seeing the sharp potential in the boy, had offered Sabo a room in the palace and private lessons with his trusted advisor Bartholomew Kuma.

Ace had met both Luffy and Sabo the following year when he had tagged along on one of his father's regular trips to East Blue, and the three of them had formed a tight bond that had only become stronger over the years.

"Hey Sabo, I bet I'm taller than you now," Ace challenged.

"Dream on," was the grinning reply.

"Why don't you take off that ridiculous hat, and we'll see?"

"I'm gonna be taller than both of you one day!" Luffy interjected loudly from where he was still squished underneath them.

"Never," the two older boys chorused, eyes twinkling as they shared a laughing look. Luffy pouted.

"I will too! Just you wait!"

There was a familiar rustling of silken skirts, and Ace tipped his head back to see the long hem of his mother's pale blue dress approaching them. Rouge smiled sweetly at the boys.

"It's lovely to see you again, Luffy, Sabo."

Luffy beamed. "Hello, Ace's Mama!"

In stark contrast to the young prince's informal manners, Sabo immediately clambered to his feet and executed a very proper bow, extending one hand with the palm upturned. Rouge's smile dimpled as she let him press a kiss to the back of her hand. "It's our honor to be here, Your Majesty," he replied with all the refined manners of a court gentleman.

Rouge sent her son a teasing look that read 'why don't you learn from Sabo now, dear' as she swept on to greet the rest of the East Blue entourage.

The boy in question turned back to see two pairs of black eyes staring at him, one simply bored and the other looking slightly betrayed.

"That was _weird_ ," Ace announced, crossing his arms.

"It's not weird!" the blond squawked defensively. "And Makino-san says it's _proper_."

Ace made a face to show exactly what he thought of that.

"Sabo tried it on Koala, and she punched him," Luffy contributed blithely.

"LUFFY!" Sabo's face was cherry red.

"How long did it take for the bruise to heal?" Ace teased.

Koala was the daughter of one of the palace cooks, and being four years older than Luffy sometimes helped Makino in tutoring the younger children. Dragon had supported Makino's suggestion of opening up group lessons to the children of the palace staff, recognizing it as good means to foster stronger ties between Luffy as the royal heir and the people. Luffy for his part had taken to the scheme with his usual exuberant enthusiasm, and learning together peers of his age had done wonders for his short attention span. Sabo would join them occasionally on top of his advanced lessons with Kuma and it was there that he had met Koala. If Luffy was to be believed, Sabo had very quickly developed a crush on the older girl and the bright color tinging the blond boy's cheeks did nothing to deny that.

Ace's question had come from the information that Koala had also been learning fishman karate from Hack lately, and any punch of hers was sure to have hurt.

"How about I punch you and we see how long _that_ takes to heal," Sabo muttered, half-threatening but also half-wry.

Ace gave him a cheeky grin in reply, cracking his knuckles with a challenging glitter in his eyes. "You wanna fight? Bring it on, I've been training with Shanks all year, I'll wipe the floor with you any day."

Sabo smirked, shifting into an offensive stance that was a mix of fishman karate and kenpo. "I wouldn't be so sure about that."

"FIGHT!" Luffy cheered.

Large calloused hands clapped down firmly on their shoulders before they could properly go at it, halting their movements.

Luffy grinned widely in greeting. "Ace's Papa!"

"Dad~ Come on~" Ace complained, squirming to get free.

Roger's grin was wide under his moustache. "It's not that I'm against seeing a good fight, but your mother would have all of our heads if you boys wreck the harbor, especially right before the Reverie. Why don't we head to the training grounds and you lot show the new recruits how it's done, huh?"

That caught Ace's attention. "Shanks is training new recruits?"

Shanks was the country's Head of Guard, in charge of sea-faring patrolling guards that worked with the support of the Marines in maintaining the peace and order through the Grand Line.

Greenhorn recruits to the palace guards and patrolling guards started out boring at first, because they mostly underestimated Ace for his age and were furthermore wary to go full out against their young prince. Something which they of course regretted instantly, because it always ended with them getting their asses wiped by a ten-year-old. But it was interesting to watch them get fired up after that first resounding defeat, and they were greatly more fun to fight the next time round. It was so much so that it had become a sort of rite of passage for the young prince of Raftel to drop in on any new training sessions, both as practice and to boost morale.

"I'm strong now too, my punch is as strong as a pistol!" Luffy proclaimed proudly.

Ace's grin was as mischievous as his father's. "We'll let Luffy at them first, they won't know what hit them."

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King Jaguar D Saul of West Blue was conversing with his retainers about the arrangements for the Reverie when he suddenly found himself with two limpets hanging off his arms and a third child beaming up at him from his side.

Two harried guards ran up a few second later, chasing futilely after their temporary charges. "Our greatest apologies, King Saul!"

The King waved their concerns off with a big laugh. "No, no, it's perfectly fine! I don't mind at all." With a wide grin the giant easily lifted his arms so that the boys hung at eye-level. "It's been too long since I've seen you three boys, look how you've all grown! Dereshishishi!"

"I'm seven now!" Luffy announced with sparkling dark eyes and a white-toothed grin as he swung his feet happily in the air.

"And so you are! A fine young man now! Dereshishishi!"

Still grinning, Ace dropped down to stand next to Sabo. Luffy, on the other hand, shimmied up Saul's arm with deft movements so that he sat perched on the giant's shoulder. The jolly-natured King took that perfectly into stride, chuckling warmly.

"Dereshishi, I was just about to go look for you boys. Come with me, there's someone I want you to meet." Saul led them over to where a young woman was stepping off the gangplank from his ship. She was perhaps in her late teens, tall and slim with shoulder-length black hair and dressed simply in a short-sleeved white cotton blouse and long burgundy skirt. She looked up at their approach, revealing dark eyes and a gentle smile.

"This is Robin!" Saul introduced cheerfully. "She's a very talented scholar from Ohara and here this year to observe the Reverie as part of her studies. I hope you boys can get along well with her."

The dark-haired girl curtsied. "It's my honor to meet you, your highnesses."

Luffy of course was the first one to react, leaning over to stick his hand out exuberantly from his perch on Saul's shoulder with a big smile. "Hiya, I'm Luffy!" If Robin was at all fazed by the informal address, she didn't show any of it as she shook Luffy's hand without hesitation.

Recalling the episode from earlier, Ace dredged up all the manners his mother had taught him, giving Robin a serious nod as he also solemnly shook her hand.

Sabo's eyes practically gleamed in his interest. "I've heard of Ohara! There's where the Tree of Knowledge is, isn't it?"

Saul smiled widely. "Indeed it is, dereshishishi! You are very well-informed, young Sabo."

"The Tree of Wazzat?" Luffy asked, cocking his head bemusedly.

Sabo stifled a sigh, but even that wasn't enough to dampen his excitement. "The Tree of Knowledge, Luffy. Makino-san told us about it before, remember? It's a huge library built inside a giant tree! Apparently it has the biggest collection of books in all the Blues, with a huge number of really rare ones! I really want to visit it someday!"

"A giant tree!? I want to go too!"

Ace grinned as well. "Sounds cool, count me in."

Sabo looked at both of them exasperatedly, knowing all too well what the two Ds were thinking of. "The Tree of Knowledge isn't for climbing!"

"Aww…"

"Dereshishishi! I'm sure you'll all get a chance to visit Ohara soon." Saul smiled good-naturedly at them, chortling. "Well now, the Reverie only starts in two days' time, so there isn't really anything for you to do today, Robin. You're free for the rest of the afternoon, so why don't you let the boys show you around the palace?"

"We can go to the gardens," Sabo suggested at the same time Luffy yelled out, "The kitchens!"

The two older boys looked at him askance. "Luffy we just had lunch!"

The young prince pouted. "That was an hour ago… I'm hungry~"

Ace and Sabo traded a helplessly fond glance. "Fine, we'll go to the kitchens to get a snack, and _then_ go to the gardens. Hey, maybe Cook can pack us a picnic too!"

"MEAT!" Luffy cheered, already running down the familiar route towards the kitchens.

"O-Oi, Luffy!"

Robin chuckled as she quickly followed the boys, leaving the sound of Saul's booming laughter behind. The Reverie was going to be even more interesting than she had expected.

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 _ **Thanks for reading! Please review!**_


	3. A Changed Destiny

**Chapter 2 – A Changed Destiny**

The area commonly known as The Gardens referred to a sprawling park adjacent to the palace. It was fully open to the public, and on weekends and holidays it was a popular relaxation spot among citizens of all ages and social status.

In one corner lay Queen Rouge's beloved flower garden, with clusters of flourishing roses in a myriad of colors and carefully tended shrubs of the Queen's favorite hibiscus flower, bright red blooms native to her homeland in South Blue. But the feature that was always the fast favorite with the young ones was really the huge hedge maze spread across half of the sizeable plot of land. Ace, Luffy and Sabo had spent many hours there in the past either chasing each other around the maze or competing to see who could get out first. While Ace had the home advantage of being more familiar with the maze, Sabo's quick mind and sharp memory made him a tough rival even without a handicap in the game.

It always amused the older boys when they had to go back into the maze to fish Luffy out, which truthfully happened more often than not.

The maze wasn't their destination for today, however, but instead it was the big grassy field that covered the rest of the garden area. The boys and Robin found a nice sunny spot to spread out the checkered picnic blanket the head cook had given them along with three generously packed wicker baskets filled with food. The Oharan scholar watched with amusement as all three boys immediately attacked the baskets just moments after sitting down, happily digging in. She selected a delicious-looking strawberry tart for herself, sitting back to enjoy the sunshine and the sound of children's laughter echoing from the maze.

It was a different kind of atmosphere from what she was used to in Ohara, where scholars practically outnumbered regular villagers. To add to that, Robin had spent most of her childhood not running around with the few other children her age but instead tucked into some alcove in the library pouring over books as her mother and Professor Clover discussed their latest project. This was different, but nice.

"So this is where you brats ended up," a familiar voice drawled from behind, cutting into their little picnic. "Stuck with babysitting duty, Robin-ya?" They turned as one to meet the crinkled dark eyes and amused smirk of their old friend. From behind the teen's lanky form, a young girl with brown twin-tails peeked out and beamed at them.

"It's Torao!" Luffy cheered around a mouthful of sandwich. "Lami too!"

Ace waved. "Hey, Law, Lami."

In contrast the other two boys, Sabo bowed his head in a respectful nod. "Prince Law, Princess Lami."

The older prince's lips twitched slightly as he dropped down casually to sit on the grass like the rest of them. "Always so formal. You know you can just call me Law like the other brats do."

Four years older and one year younger than Ace and Sabo respectively, the prince and princess of North Blue's Trafalgar D royal family were familiar playmates to the young princes, especially given that neither the Jaguar nor Portgas family lines had children near their age.

Instead of sitting down immediately like her brother, Lami instead ran around their little circle to hug Robin. The older girl returned the greeting warmly. "It's good to see you again, princess."

The three boys looked between Law, Lami and Robin. "You know each other?"

"Robin stayed with us all of last year!" Lami chimed up as she took a seat between her brother and Robin, folding her feet under her in an attempt to imitate the older girl's graceful posture. "Robin's really, really smart," she added. "She's an _archaeologist_ , and she's almost as good as Big Brother at reading the poneglyphs."

That caught Ace and Sabo's attention. "The poneglyphs?"

"What are poneglifs?" Luffy piped up, head tilted as he chewed. "Are they good to eat?"

"Poneglyphs are not food, Luffy," Sabo returned with the resigned patience of one long used to the smaller boy's ways. "Dragon-san has been teaching you how to read them since last year, remember?"

"Ohh. The mystery letter thingies."

"But I thought only the descendants of the D families are taught how to read the poneglyphs?" Sabo questioned towards Robin, curious.

Robin inclined her head in acknowledgement. "That is correct for most part, and is also what is most commonly known to the public. However, to be accurate, two other groups of people aside from the descendants of the Great Kingdom are taught how to decipher the secret poneglyphs – direct descendants of the Kozuki clan, the stonemasons who etched the first poneglyphs; and select scholars of Ohara, each who have sworn an oath only to use the knowledge for scholarly purpose. I qualified to be one of them not too long ago, and was sent to North Blue to further my studies."

Sabo could guess, even though she didn't mention it, what a feat it was for her to have been qualified so young. A group such as that must surely be brilliantly exclusive, after all.

"But what poneglifs for?"

All eyes turned towards the youngest prince. "You really don't know, Luffy?"

"Can you tell us the story about the poneglyphs again, Robin?" Lami suggested brightly. "Robin's really good at telling stories," she told the boys. "I miss hearing them."

"What, my stories aren't good enough for you, Lami?" Law interjected teasingly.

Much to the two older youths' amusement, the girl was immediately contrite, sending puppy-eyes to her brother who gently flicked her cheek to show he had been teasing.

"Well then, if you would like to hear it, I'm happy to do so…" Robin smiled as the younger children nodded eagerly, sprawling down in more comfortable positions across the picnic blanket. The wind rustled softly through her hair as she started the tale, as if in gentle encouragement as well.

"This is a story that started long ago, with the Great King D himself. King D had travelled widely across all the seas in his time, encountering all sort of wonders, some of which no one else had ever seen. He found lands where summer and winter could change in an instant; islands where time had stood still; mysteries which had sunk beneath the waters. He dove down to the furthest depths of the sea and befriended the mermaid princess, Poseidon; flew up to the clouds where he met the majestic creature of flight, Uranus. At the end of his travels he returned back to the Grand Line where he built his great empire of peace, so loved by the people that they referred to it as the Great Kingdom.

The legend continues centuries later, long after King D's passing, during the Uprising of the Twenty Kingdoms. Descendants of former vassals of King D rose up to rebel against the rule of the Great Kingdom, bringing an unspeakable power that spread terror wherever they landed. The descendants of King D called on a hundred of the best shipwrights from Water 7 to build the great warship Pluton, but even then they were no match for the malevolent weapons of the Twenty Kingdoms.

It was in this time of great danger that Poseidon rose from the sea to their aid, bringing with her the great Sea Kings from the very depths of the sea floor, where the sea creatures grew larger and stronger than any surface dwellers had ever seen. The Sea Kings circled around the besieged islands, shielding them from further harm. Then down from the sky soared Uranus on wings of fire, and together they successfully quelled the destruction wrought by the Twenty Kingdoms.

With the defeat of the Twenty Kingdoms, the world settled back to its peace. The warship Pluton, having completed its purpose, was hidden away; and Poseidon returned home to the sea and Uranus to the sky.

But before their departure both Poseidon and Uranus left parting words with the Descendant Kings of D, instructions on how they could be summoned again should another great peril befall the world. These instructions, along with the resting place of Pluton, were transcribed by a trusted family of stonemasons upon great stone slabs, to be preserved for future generations long past the Kings' deaths. To prevent such great knowledge from falling into the wrong hands, the Kings crafted a secret language, the poneglyphs, which is now passed down from parent to child among the descendants of King D. The stones themselves were scattered across the seas, each guarded carefully by loyal vassals. It is the wish of all humankind that we never be faced again with such a calamity to need to draw upon the power of the Ancients, but what they left with us is the reassurance that they will once again come to aid us should such a misfortune arise. And it is thus through the power of the Ancients that our peace was preserved till this day, just like King D had envisioned when he built his kingdom upon the endless horizon of the blues."

Robin smiled warmly at the rapt attention all the children were giving her even after she gently closed her story.

Ace's eyes were bright with interest and curiosity. "But there are more than just three stones, right?"

Robin nodded. "The Kings had additional stones carved as well, partly as decoys for the real Stones but also to maintain historical notes in a more lasting form than ink on paper. The stone at Ohara, for one, contains the history of how the great library was built, and there is another supposedly on Fishman Island, though I have not yet seen it for myself, which tells of how the ship Noah was brought to the surface by Poseidon's power."

"So the mystery letters are a mystery language about the Mystery People," Luffy summed up comprehensively, tapping one fist against his palm in an epiphany.

A brief silence followed as all of them stared at the small boy, before everyone simultaneously burst out laughing.

"Well if you want to put it that way, it really isn't too far off," Ace conceded, grinning as he leaned against Sabo, both of them having toppled over into each other from laughing too hard.

Law shook his head with a fond grin still quirking his lips. The younger boy never failed to catch him off guard.

Their laughter echoed across the grounds, bright and sweet, drawing the attention of the citizens also relaxing around the gardens. The people smiled, waving warmly to their young prince when Ace looked their way, which he (and an ever-enthusiastic Luffy as well) returned without reservation.

 _A kind and just ruler, King D loved his people and was much beloved in return._

The Kingdoms of D were at peace.

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 _ **Please do leave a review!**_

 _ **PS - Updates will still be slow-going with me focusing mostly on "From the Decks of the Sunny" for now, but rest assured that I do have more chapters for this story in the works.**_ _ **The chapters so far have largely been world-building and character-introduction chapters, but we'll be having a major time-skip in probably 2 chapters' time where we'll then properly kick off the plot, so do stay tuned for that!**_

 _ **Till next time! Merry Christmas, Happy New Year and Happy Holidays to all!**_


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